UPDATE: just to be sure I followed #2 suggested by Michael Sartain again and no-go.
As for item #3:
I proceeded to build (unknowingly) the whole llvm toolchain (which took like 12 hours on a single core) that had clang-13. Along with that, I made the following change to the Engine/Extras/ThirdPartyNotUE/SDKs/HostLinux/Linux_x64/v17_clang-10.0.1-centos7/x86_64-unknown-linux-gnu’ file:
else if ((CompilerVersionMajor 10 + CompilerVersionMinor) > 130 || (CompilerVersionMajor * 10 + CompilerVersionMinor) < 60)
I then proceeded to set the LINUX_MULTIARCH_ROOT environment variable to point to the llvm folder, but during the build of UE4, it wasn’t able to detect clang. I attempted to compare the directory structure of the v17_clang-10.0.1-centos7 file that gets used when building UE4 v4.26 but I wasn’t sure how to change the llvm structure to match it or if that was even the right thing to do.
Anyways, I never got it working. I don’t mind working in v4.25, but everyone else at work is using the Windows version of UE4 with v4.26 and I cannot use any of their environments. Maybe one day but not today…